Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove the condensate trap from the boiler

Observation:

Note:
The condensate trap will contain liquid, ensure the work area and electrical parts of the boiler are protected when removing the trap.
Inspect the inlet and outlet connections of the trap for blockages or restrictions
Refit the trap after the inspection, when refitting ensure the trap is refilled to the required level with tap water.